Using volcanic pumice dust to produce high-strength self-curing concrete in hot weather regions

The aim of this research is to investigate the influence of cement mass replacement with volcanic pumice dust (VPD) at levels of 10 %, 20 %, and 30 % on the performance of high-strength concrete (HSC) under submerging (SuC) and internal curing (InC) methods up to 180 days of age in hot weather climates. Two curing techniques were tested in this study in hot weather climates: (i) the specimens were submerged in a water container inside lab conditions and (ii) the specimens were left outdoors uncured until the day of the test. The fresh properties (slump test) and hardened properties (i.e., compressive, splitting tensile, and flexural strength), as well as water absorption, sorptivity, and microstructure (thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy), were evaluated experimentally. At age 180 days, application of the InC technique preserved compressive strength in the range of 74.5–85.8 % versus SuC for all replacement levels; meanwhile, this technique preserved splitting tensile and flexural strengths in the range of 86.8–93.1 % and 77.0–90.1 %, respectively. Utilizing VPD improved the permeability qualities by decreasing the water absorption ratio compared with the control specimen at all test ages. Despite the decrease in the hardened concrete characteristics, the application of InC achieves acceptable results compared with the amount of water that will be saved, especially in hot weather.